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Biology & Management of Biology & Management of Brown Root Rot of AlfalfaBrown Root Rot of Alfalfa
F.A. Gray, C.R. Hollingsworth, D.W. KochR.W. Groose and R.C. Larsen
Anamorphic (asexual) stage: Phoma sclerotioides
(syn. Plenodomus meliloti & Plenodomus sclerotioides)
Fungal Taxonomy
8-wk-old culture on PDA
Pycnidia (SEM, 110x) Hyaline, single-celled conidia (400x)
History
1933-1st reported on sweet clover in Canada
1984 – widespread on alfalfa in the Peace River Valley of Alberta
1996 – 1st reported on alfalfa in the U.S. in Wyoming
Host Range
Alfalfa
Alsike Clover
Bird’s-Foot Trefoil
Red Clover
Sainfoin
Sweet Clover
(J.G.N Davidson)
Survival & Spread
- Survival: in plant debris & in soil
- Spread: by wind & grazing animals
(J.G.N Davidson)
Diagnosis
Farson, Wyoming Spring of 1996
Severe Winterkill
Plants removed showing severe root rot
Close up of dead and dying plants
a. Plant Symptoms
Dead
Diseased
Diagnosis
b. Root isolation
c. PCR-based SCAR markers (R.C. Larsen, USDA-ARS, Prosser, WA)
Root isolation on PDA at 500 F. after 8 weeks
Note white mycelium, black pycnidia and yellow spore masses
Distribution
Currently known distribution in the U.S.
(Idaho, Montana, Wisconsin, Wyoming)
CANADAIndigenous Fungus
USA
Recommended Control Practices in Canada
1. Crop rotation – Grow annual crops such as oats or barley for 3 years between alfalfa crops. Avoid rotation with other forage legume crops especially sweet clover.
2. Harvesting/Grazing Management
- Avoid excessive cutting
- Avoid late fall cutting
- Avoid overgrazing & grazing in the fall before the ground is frozen.
3. Maintain proper soil fertility
4. Plant a resistant variety
- The variety Anik
(Medicago falcata) is
partially resistant.
- The variety Peace is the
least susceptible of the
M. sativa varieties
J.G.N Davidson.
AnikPeace
Farson, Wyoming
Recommended ControlPractices in the USA
1. Same as for Canada (items 1, 2, and 3)
2. Reaction of most U.S. varieties to BRR is currently unknown
3. The variety “Peace” performed well in the presence of BRR at Farson, Wyoming but may be susceptible to other major stand decline diseases in the U.S.
4. Other varieties performing well in the presence of BRR at Farson include: Ranger, Avalanche + Z and Spreador 3
Other available information on Brown Root Rot:
a. University of Wyoming Bulletin, B-1136, “Brown Root Rot of Alfalfa”
b. BRR Evaluation Protocol for, “Standard Tests to Characterize Alfalfa Cultivars” (pending final approval)